1. Field of the Invention
The present invention relates to a process for the production of dihomo-.gamma.-linolenic acid (DGLA) and a lipid containing DGLA by fermentation using a microorganism capable of producing arachidonic acid (ARA) and having reduced or lost .DELTA.5 desaturation activity.
2. Related Art
DGLA, also known as 8,11,14-eicosatrienoic acid, is known to be present as a constituent fatty acid of fish oils and seaweeds. However, because of the low content of DGLA in fish oils and the like, a purified DGLA product obtained from fish oils and seaweeds is expensive. As relatively efficient production processes, there are fermentation methods using a microorganism capable of producing DGLA (Japanese Unexamined Patent Publication No. 63-14696), methods providing enhanced productivity by adding an additive, such as an unsaturated fatty acid (Japanese Unexamined Patent Publication Nos. 64-47384, and 64-47385), and methods using sesame oil, one of various plant extracts, sesamin, episesamin or the like (Japanese Unexamined Patent Publication Nos. 1-243992, 2-268690, 3-72892 and 3-49688).
Various studies have been carried out regarding the actions of essential fatty acids on an organism, and it is known that in many cases eicosanoids derived from DGLA and ARA are antagonistic. Although it is known that a group of prostaglandin 1 group derived from DGLA exhibit platelet anti-coagulation action, vasodilation activity, bronchdilation activity anti-inflammatory action, and the like, for DGLA orally taken as a fat or oil in foods so as to exhibit the above-mentioned actions, DGLA-containing oil or fat product that has a low content of ARA antagonistic to DGLA is most preferable. Moreover, in the case wherein DGLA is purified from a DGLA-containing fat or oil, a DGLA-containing fat or oil having a low content of ARA is preferable as a starting material. Thus, the development of DGLA-containing fat or oil having a low content of ARA is in urgent demand, but a process for the production of such a fat or oil is not known.